ex_aws VS guardian

If you want to upload files from the server, please check out ex_aws, ex_aws_s3, and AWS S3 in Elixir with ExAws. Uploading from the server is very straightforward compared to uploading from the client mainly because ex_aws already includes all necessary request settings. If you want the user to first upload the file to the server (maybe you want to change the file a bit before storing it or generating thumbnail of the picture), then consider also using Waffle that comes with seamless integration with ex_aws.

We will use the library ex_aws to manage all the AWS resources

AWS: I don't have a definitive answer for you on AWS. I've used ex_aws a good bit, and it's reasonably solid. aws-elixir also seems to be actively maintained.

Prepare your account, we will use AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY. Please visit here for more information about ExAWS: https://github.com/ex-aws/ex_aws

- https://github.com/ex-aws/ex_aws

As for the original question, OP you should check out https://github.com/ueberauth/guardian if you want to roll your own auth. If not rolling you own you can just use a standard Oauth provider and validate their tokens (surprise they are JWTs) in you backend using their public keys.

AuthN: For authentication, I'd look at the built-in auth generator. If you need to add JWT things, joken and/or guardian can probably meet your needs.